PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.BareTraps Astaire Off White Canvas Slip on Fisherman Shoe NEW , Born Women’s Size 11 Brown Closed Back Clogs Mint Condition Pre Owned , KELLY & KATIE BROWN LEATHER LOAFER WOMENS SHOE SIZE 8M(US)Women's Sperry Top Siders Tan leather with cotton checkered design Size 6.5Mwomens skechers taupe leather slip on cross strap shoes size 6 , Crocs Slip-On Loafers Flats Casual Dress Comfort Mocassin Women's Size:See NoteBertie Silver Sparkle Slip On ShoesKEEN Kaci Sz 9.5 Brown Leather Slip On Walking Comfort Shoe Laser Cut Flower oe3 , Blue by Betsey Johnson Women's SB-Edith Ballet Flat, Silver (Size 5 B(M) US)Ladies Hushpuppy 'Soft Style' Shoes, Black Pumps, 11E, Dressy and SophisticatedJeffrey Campbell Red Daroca Size 40 , Clarks Candra Ballet Flat - Women's Size 7, Black , Franco Sarto Womens Sullivan Leather Pointed Toe Ballet Flats, Beige, Size 6.0 X , A35 Aleaa Ballet Flats 550, Cognac, 8 US , Polar Women's Casual Slip-On Shoes - Black - Size 8 , ***NEW***Bensimon Canvas Hi Top Tennis Shoes BrownAsics 8 Running Shoes Athletic Gel Strike Gray Pink T9D9Q Women's , Womens SAUCONY ProGrid Guide 6 Size US 9 Blue/Coral Running Shoes 10179-6 , Keen Voyageur Hiking Trail Shoes Women's Size 8 Athletic GrayAhnu Suede And Leather Burgundy Size 7W. GOOD!! , Saucony Womens S15269-18 Black Running, Cross Training Shoes Size 8.5 MSkechers D'Lites Women's Size 6.5 Black/White Reinvention Athletic Shoes F1-309Skechers Active 22126/BKCC Size 9.5 black / CharcoalNew Nike Revolution 3 Womens 819303-003 Violet purple teal Running Shoes Sz 8.5Adidas Women's Supernova BB3104 Athletic Running Shoes Blue/White/CoralVans SK8 HI SLIM Studs Marshmallow/Black Women's Shoes 6 , XS / 5 - 6 - NIKE Purple Venom STUDIO WRAP 2 Elastic Dance Yoga Shoes NEW 0000MBReebok Fabulista MID II Women's Black Leather Sports Shoes Hi Tops Sneakers , Asics Gel Contend Sz 6.5 Women Silver Purple Running Shoes Mint YGI A8 , NEW BALANCE MINIMUS WT20BP2 Athletic Minimalist Running Women's Shoes Size US 7 ,
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."